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+/*
+ * Copyright (c) 2000-2003 Silicon Graphics, Inc. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * Further, this software is distributed without any warranty that it is
+ * free of the rightful claim of any third person regarding infringement
+ * or the like. Any license provided herein, whether implied or
+ * otherwise, applies only to this software file. Patent licenses, if
+ * any, provided herein do not apply to combinations of this program with
+ * other software, or any other product whatsoever.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write the Free Software Foundation, Inc., 59
+ * Temple Place - Suite 330, Boston MA 02111-1307, USA.
+ *
+ * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
+ * Mountain View, CA 94043, or:
+ *
+ * http://www.sgi.com
+ *
+ * For further information regarding this notice, see:
+ *
+ * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
+ */
+#ifndef __XFS_BEHAVIOR_H__
+#define __XFS_BEHAVIOR_H__
+
+/*
+ * Header file used to associate behaviors with virtualized objects.
+ *
+ * A virtualized object is an internal, virtualized representation of
+ * OS entities such as persistent files, processes, or sockets. Examples
+ * of virtualized objects include vnodes, vprocs, and vsockets. Often
+ * a virtualized object is referred to simply as an "object."
+ *
+ * A behavior is essentially an implementation layer associated with
+ * an object. Multiple behaviors for an object are chained together,
+ * the order of chaining determining the order of invocation. Each
+ * behavior of a given object implements the same set of interfaces
+ * (e.g., the VOP interfaces).
+ *
+ * Behaviors may be dynamically inserted into an object's behavior chain,
+ * such that the addition is transparent to consumers that already have
+ * references to the object. Typically, a given behavior will be inserted
+ * at a particular location in the behavior chain. Insertion of new
+ * behaviors is synchronized with operations-in-progress (oip's) so that
+ * the oip's always see a consistent view of the chain.
+ *
+ * The term "interpostion" is used to refer to the act of inserting
+ * a behavior such that it interposes on (i.e., is inserted in front
+ * of) a particular other behavior. A key example of this is when a
+ * system implementing distributed single system image wishes to
+ * interpose a distribution layer (providing distributed coherency)
+ * in front of an object that is otherwise only accessed locally.
+ *
+ * Note that the traditional vnode/inode combination is simply a virtualized
+ * object that has exactly one associated behavior.
+ *
+ * Behavior synchronization is logic which is necessary under certain
+ * circumstances that there is no conflict between ongoing operations
+ * traversing the behavior chain and those dunamically modifying the
+ * behavior chain. Because behavior synchronization adds extra overhead
+ * to virtual operation invocation, we want to restrict, as much as
+ * we can, the requirement for this extra code, to those situations
+ * in which it is truly necessary.
+ *
+ * Behavior synchronization is needed whenever there's at least one class
+ * of object in the system for which:
+ * 1) multiple behaviors for a given object are supported,
+ * -- AND --
+ * 2a) insertion of a new behavior can happen dynamically at any time during
+ * the life of an active object,
+ * -- AND --
+ * 3a) insertion of a new behavior needs to synchronize with existing
+ * ops-in-progress.
+ * -- OR --
+ * 3b) multiple different behaviors can be dynamically inserted at
+ * any time during the life of an active object
+ * -- OR --
+ * 3c) removal of a behavior can occur at any time during the life of
+ * an active object.
+ * -- OR --
+ * 2b) removal of a behavior can occur at any time during the life of an
+ * active object
+ *
+ */
+
+struct bhv_head_lock;
+
+/*
+ * Behavior head. Head of the chain of behaviors.
+ * Contained within each virtualized object data structure.
+ */
+typedef struct bhv_head {
+ struct bhv_desc *bh_first; /* first behavior in chain */
+ struct bhv_head_lock *bh_lockp; /* pointer to lock info struct */
+} bhv_head_t;
+
+/*
+ * Behavior descriptor. Descriptor associated with each behavior.
+ * Contained within the behavior's private data structure.
+ */
+typedef struct bhv_desc {
+ void *bd_pdata; /* private data for this behavior */
+ void *bd_vobj; /* virtual object associated with */
+ void *bd_ops; /* ops for this behavior */
+ struct bhv_desc *bd_next; /* next behavior in chain */
+} bhv_desc_t;
+
+/*
+ * Behavior identity field. A behavior's identity determines the position
+ * where it lives within a behavior chain, and it's always the first field
+ * of the behavior's ops vector. The optional id field further identifies the
+ * subsystem responsible for the behavior.
+ */
+typedef struct bhv_identity {
+ __u16 bi_id; /* owning subsystem id */
+ __u16 bi_position; /* position in chain */
+} bhv_identity_t;
+
+typedef bhv_identity_t bhv_position_t;
+
+#define BHV_IDENTITY_INIT(id,pos) {id, pos}
+#define BHV_IDENTITY_INIT_POSITION(pos) BHV_IDENTITY_INIT(0, pos)
+
+/*
+ * Define boundaries of position values.
+ */
+#define BHV_POSITION_INVALID 0 /* invalid position number */
+#define BHV_POSITION_BASE 1 /* base (last) implementation layer */
+#define BHV_POSITION_TOP 63 /* top (first) implementation layer */
+
+/*
+ * Plumbing macros.
+ */
+#define BHV_HEAD_FIRST(bhp) (ASSERT((bhp)->bh_first), (bhp)->bh_first)
+#define BHV_NEXT(bdp) (ASSERT((bdp)->bd_next), (bdp)->bd_next)
+#define BHV_NEXTNULL(bdp) ((bdp)->bd_next)
+#define BHV_VOBJ(bdp) (ASSERT((bdp)->bd_vobj), (bdp)->bd_vobj)
+#define BHV_VOBJNULL(bdp) ((bdp)->bd_vobj)
+#define BHV_PDATA(bdp) (bdp)->bd_pdata
+#define BHV_OPS(bdp) (bdp)->bd_ops
+#define BHV_IDENTITY(bdp) ((bhv_identity_t *)(bdp)->bd_ops)
+#define BHV_POSITION(bdp) (BHV_IDENTITY(bdp)->bi_position)
+
+extern void bhv_head_init(bhv_head_t *, char *);
+extern void bhv_head_destroy(bhv_head_t *);
+extern int bhv_insert(bhv_head_t *, bhv_desc_t *);
+extern void bhv_insert_initial(bhv_head_t *, bhv_desc_t *);
+
+/*
+ * Initialize a new behavior descriptor.
+ * Arguments:
+ * bdp - pointer to behavior descriptor
+ * pdata - pointer to behavior's private data
+ * vobj - pointer to associated virtual object
+ * ops - pointer to ops for this behavior
+ */
+#define bhv_desc_init(bdp, pdata, vobj, ops) \
+ { \
+ (bdp)->bd_pdata = pdata; \
+ (bdp)->bd_vobj = vobj; \
+ (bdp)->bd_ops = ops; \
+ (bdp)->bd_next = NULL; \
+ }
+
+/*
+ * Remove a behavior descriptor from a behavior chain.
+ */
+#define bhv_remove(bhp, bdp) \
+ { \
+ if ((bhp)->bh_first == (bdp)) { \
+ /* \
+ * Remove from front of chain. \
+ * Atomic wrt oip's. \
+ */ \
+ (bhp)->bh_first = (bdp)->bd_next; \
+ } else { \
+ /* remove from non-front of chain */ \
+ bhv_remove_not_first(bhp, bdp); \
+ } \
+ (bdp)->bd_vobj = NULL; \
+ }
+
+/*
+ * Behavior module prototypes.
+ */
+extern void bhv_remove_not_first(bhv_head_t *bhp, bhv_desc_t *bdp);
+extern bhv_desc_t * bhv_lookup(bhv_head_t *bhp, void *ops);
+extern bhv_desc_t * bhv_lookup_range(bhv_head_t *bhp, int low, int high);
+extern bhv_desc_t * bhv_base(bhv_head_t *bhp);
+
+/* No bhv locking on Linux */
+#define bhv_lookup_unlocked bhv_lookup
+#define bhv_base_unlocked bhv_base
+
+#endif /* __XFS_BEHAVIOR_H__ */
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